Process for refining crude resin for electronic material

ABSTRACT

A process is provided for effectively removing by-products such as oligomers contained within a crude resin for an electronic material, thus producing a resin for an electronic material. In this process, a crude resin for an electronic material containing (a1) structural units derived from a (meth)acrylate ester with a hydrophilic site is washed using (b1) an organic solvent which is capable of dissolving said crude resin for an electronic material and which separates into two layers when combined with water, and (b2) water.

TECHNICAL FIELD

The present invention relates to a process for refining a crude resinfor an electronic material, a resin for an electronic material producedby such a refining process, a process for producing a chemicallyamplified photoresist composition using such a resin for an electronicmaterial, and a chemically amplified photoresist composition comprisingsuch a resin for an electronic material.

BACKGROUND ART

Typical examples of electronic material resins that are used as theresin component of photoresists used during the production of electronicdevices such as semiconductor elements, liquid crystal elements andmagnetic heads and the like include polyhydroxystyrene based resins(such as resins in which a portion of the hydroxyl groups are protectedwith acid dissociable, dissolution inhibiting groups, copolymers ofhydroxystyrene units and styrene units, and copolymers of hydroxystyreneunits and (meth)acrylate esters) in the case of KrF resist resins, and(meth)acrylate ester copolymer based resins in the case of ArF resistresins.

Examples of processes for refining these types of electronic materialresins include the processes disclosed in the patent reference 1 listedbelow in the case of the former type polyhydroxystyrene based resins,and the processes disclosed in the patent reference 2 listed below inthe case of the latter type (meth)acrylate ester copolymer based resins.

The patent reference 1 discloses a process in which the resin isdissolved in a polar solvent such as N-methylpyrrolidone and analiphatic hydrocarbon based solvent, and following phase separation theresin is obtained from the polar solvent layer, as well as a process inwhich the resin is dissolved in a lower alcohol, and is then added to apoor solvent such as water to precipitate the polymer.

The patent reference 2 discloses a process in which the resin is refinedusing an aliphatic hydrocarbon such as n-hexane, or a mixed solvent ofan aliphatic hydrocarbon and ethyl acetate.

Patent Reference 1: Japanese Unexamined Patent Application, FirstPublication No. Hei 6-289614

Patent Reference 2: Japanese Unexamined Patent Application, FirstPublication No. 2002-201232

However, when a crude resin for an electronic material containingstructural units derived from a (meth)acrylate ester with a hydrophilicsite such as a lactone is refined using these types of processes, evenif the unreacted monomer is able to removed to some extent, the removalof materials of comparatively high polarity such as by-product oligomersor low molecular weight polymers is particularly difficult.Consequently, the use of resins containing these types of by-productsthat are difficult to remove as components of electronic materials isunavoidable.

For example, when an ArF chemically amplified photoresist composition isprepared using a resin containing by-products such as the oligomers andthe like described above, although the various characteristics such asthe sensitivity, the resolution, and the resist pattern shape aresatisfactory, the number of defects (surface defects) in the resistpattern following developing can become problematic. These defects referto general problems such as scum and bridging between resist patternsdetected by inspecting the developed resist pattern from directlyoverhead using a surface defect observation apparatus manufactured byKLA Tencor Corporation (brand name “KLA”).

Furthermore, during storage as a resist solution (a photoresistcomposition in solution form), problems may also develop in terms of thestorage stability as a resist solution, resulting in the development offine particles in the solution. Moreover, if these fine particlesdevelop, they can cause the type of defects described above, meaningimprovements in the storage stability as a resist solution are needed inorder to improve the level of defects.

DISCLOSURE OF INVENTION

The present invention takes the above problems associated with theconventional art into consideration, with an object of providing aprocess for refining a crude resin for an electronic material thatenables the effective removal of by-products such as oligomers containedwithin the crude resin for an electronic material, as well as a resinfor an electronic material produced by such a refining process, aprocess for producing a chemically amplified photoresist compositionusing such a resin for an electronic material, and a chemicallyamplified photoresist composition comprising such a resin for anelectronic material.

Furthermore, in the aspect of the invention relating to a chemicallyamplified photoresist composition, the present invention has an objectof improving the level of defects and the storage stability as a resistsolution, without impairing characteristics such as the resolution, theresist pattern shape and the sensitivity.

As a result of intensive investigations aimed at resolving the aboveproblems, the inventors of the present invention discovered that bywashing a crude resin for an electronic material containing (a1)structural units derived from a (meth)acrylate ester with a hydrophilicsite using (b1) an organic solvent which is capable of dissolving thecrude resin for an electronic material and which separates into twolayers when combined with water, and (b2) water, the problems describedabove could be resolved, and they were hence able to complete thepresent invention.

In other words, a first aspect of the present invention is a process forrefining a crude resin for an electronic material, wherein a crude resinfor an electronic material containing (a1) structural units derived froma (meth)acrylate ester with a hydrophilic site is washed using (b1) anorganic solvent which is capable of dissolving the crude resin for anelectronic material and which separates into two layers when combinedwith water, and (b2) water.

A second aspect of the present invention is a resin for an electronicmaterial produced by the above refining process.

A third aspect of the present invention is a process for producing achemically amplified photoresist composition using an aforementionedresin for an electronic material.

A fourth aspect of the present invention is a chemically amplifiedphotoresist composition comprising an aforementioned resin for anelectronic material.

The term “(meth)acrylic acid” refers to either one of, or both,methacrylic acid and acrylic acid. The term “structural unit” refers toa monomer unit that contributes to the formation of a polymer. The term“lactone unit” refers to a group in which one hydrogen atom has beenremoved from a monocyclic or polycyclic lactone. The term “crude resinfor an electronic material” describes a resin in the unrefined stateimmediately following polymerization of a resin for use in thepreparation of electronic devices such as semiconductor elements, liquidcrystal elements and magnetic heads and the like.

According to the present invention, there are provided a process forrefining a crude resin for an electronic material that enables theeffective removal of by-products such as oligomers contained within thecrude resin for an electronic material, as well a resin for anelectronic material produced by such a refining process, a process forproducing a chemically amplified photoresist composition using such aresin for an electronic material, and a chemically amplified photoresistcomposition comprising such a resin for an electronic material.

BEST MODE FOR CARRYING OUT THE INVENTION

As follows is a sequential description of one example of a process forrefining a crude resin for an electronic material according to thepresent invention.

First, a crude resin is prepared by a typical polymerization reaction.In other words, at least one monomer that generates the structural unitsof the target resin is first dissolved in a typical polymerizationsolvent. Examples of typical polymerization solvents includetetrahydrofuran, dioxane, and methyl ethyl ketone. Next, a knownpolymerization initiator such as azobisisobutyronitrile is added to thesolution, and the polymerization is conducted by heating, preferably at50 to 80° C. for a period of 2 to 6 hours.

In a refining process of the present invention, (i) a crude resin for anelectronic material produced at the completion of the abovepolymerization reaction, which contains (a1) structural units derivedfrom a (meth)acrylate ester with a hydrophilic site is (ii) washed using(b1) an organic solvent which is capable of dissolving the crude resinfor an electronic material and which separates into two layers whencombined with water, and (b2) water. The washing step defined in (ii)above is described as the washing step of the present invention.

Either prior to, following, or both prior to and following the washingstep of the present invention, the resin may be further washed using ahydrophobic solvent (hereafter referred to as a hydrophobic solventwashing step).

Providing a hydrophobic solvent washing step prior to the washing stepof the present invention is preferred, as both unreacted monomers, andoligomer and low molecular weight polymer by-products can be removed,enabling a further improvement in the defect reduction effect.

As follows is a description of the case in which an aforementionedhydrophobic solvent washing step and a washing step of the presentinvention are conducted sequentially.

In the hydrophobic solvent washing step, the reaction liquid containinga dissolved first crude resin that is generated at the completion of thepolymerization reaction is poured into a hydrophobic solvent. Examplesof suitable hydrophobic solvents include aliphatic hydrocarbons such aspentane, 2-methylbutane, n-hexane, 2-methylpentane, 2,2-dibutylbutane,2,3-dibutylbutane, n-heptane, n-octane, isooctane,2,2,3-trimethylpentane, n-nonane, 2,2,5-trimethylhexane, n-decane andn-dodecane, and of these, n-hexane and n-heptane are particularlypreferred. A quantity of the hydrophobic solvent equivalent to at least2-fold the mass, and preferably from 4 to 5-fold the mass of thepolymerization solvent enables better removal of impurities such as theunreacted monomer, and is consequently preferred. Following the pouringof the first crude resin into the hydrophobic solvent, the mixture ispreferably stirred or shaken at 10 to 40° C., and preferably from 20 to30° C., for a period of 10 to 60 minutes, and preferably from 25 to 35minutes, thereby precipitating the crude resin as a solid. A secondcrude resin is obtained by filtering off this precipitated solid.

By providing this type of hydrophobic solvent washing step, the majorityof the unreacted monomer from the polymerization reaction can bedissolved in the hydrophobic solvent and removed.

This hydrophobic solvent washing step can also be repeated if necessary.In other words, the second crude resin obtained in the hydrophobicsolvent washing step can be redissolved in a polymerization solvent suchas tetrahydrofuran, and the operation of adding more of the hydrophobicsolvent and then filtering off the precipitated crude resin can berepeated.

Next, the second crude resin obtained in the hydrophobic solvent washingstep is transferred to the washing step of the present invention. Inthis step, first the second crude resin is dissolved in (b1) an organicsolvent which is capable of dissolving the above crude resin for anelectronic material and which separates into two layers when combinedwith water. The concentration of the thus prepared solution of thesecond crude resin in this organic solvent (b1) is preferably within arange from 5 to 10% by weight, and even more preferably from 6 to 8% byweight. By ensuring a concentration within this range, the separation ofthe solvent layer from the water layer, and the degree of removal ofimpurities such as oligomers can both be improved.

Subsequently, water is poured into the solution of this organic solvent(b1). There are no particular restrictions on the relative quantities(the weight ratio) of the organic solvent (b1) and water, providedseparation into two layers is possible, although an organic solvent(b1): water ratio within a range from 1:1 to 4:1 is preferred, and aratio from 2:1 to 3:1 is even more desirable. If the proportion of wateris less than a 4:1 ratio, then an adequate washing effect cannot berealized, whereas if the ratio exceeds 1:1, the quantity of the organicsolvent (b1) that dissolves in the water increases, thereby increasingthe quantity of the target resin that is removed with the water layer,and thus reducing the yield, reducing productivity, and increasingcosts.

Because a more satisfactory washing effect is achieved by firstdissolving the second crude resin in the organic solvent (b1), asolution of the organic solvent (b1) is preferably prepared prior to thewashing process.

Following the pouring of water into the solution of the second cruderesin in the organic solvent (b1), the mixture is preferably stirred orshaken at 10 to 40° C., and preferably from 20 to 30° C., for a periodof 10 to 60 minutes, and preferably from 25 to 35 minutes to effect thewashing process.

Subsequently, when the stirring is halted and the liquid is allowed tosettle, a two layer system develops with the layer of the organicsolvent (b1) as the top layer and the water layer as the bottom layer.By removing the bottom water layer from this two layer system, asolution of the target resin for an electronic material dissolved in theorganic solvent (b1) can be obtained. Repeated washing may then beconducted by pouring in additional water, and this washing operation ispreferably repeated at least two times.

Subsequently, the electronic material resin can be produced byconcentrating the solution of the electronic material resin in theorganic solvent (b1), and then performing an additional distillationprocess or the like to remove any remaining water. The electronicmaterial resin can either be obtained as a solid, or retained and usedas a solution in the organic solvent (b1), as is required in theproduction of a chemically amplified photoresist.

By providing a washing step of the present invention as described above,oligomers and low molecular weight polymers, and particularly oligomersand low molecular weight polymers with a comparatively high polarity canbe dissolved in the water layer and removed.

There are no particular restrictions on the organic solvent (b1) used inthe washing step of the present invention, provided the solvent iscapable of dissolving the above crude resin for an electronic material,and separates into two layers when combined with water, or in otherwords, is a solvent that is suitable for use in a two layerliquid-liquid washing process with water.

Examples of suitable organic solvents include glycol ether esters,esters and ketones. Specific examples include glycol ether esters suchas propylene glycol monoalkyl ether acetates, esters such as ethylacetate, butyl acetate and isoamyl acetate, and ketones such as2-heptanone, methyl ethyl ketone, methyl isobutyl ketone, andcyclohexanone. These solvents can be used singularly, or in mixtures oftwo or more solvents.

Of the above solvents, propylene glycol monoalkyl ether acetates arepreferred, as they offer a superior removal effect for oligomers and lowmolecular weight polymers, and particularly oligomers and low molecularweight polymers with a comparatively high polarity, contained within thecrude resin. In those cases in which the resin is used as a chemicallyamplified photoresist composition, propylene glycol monomethyl etheracetate (PGMEA) is particularly preferred as it provides good safetylevels for the resist solvent, superior resist characteristics such asresolution and pattern shape, and also enables a high level ofefficiency in the resist preparation process. Suitable examples of thealkyl group in the propylene glycol monoalkyl ether acetate includelower alkyl groups such as methyl groups, ethyl groups, propyl groupsand butyl groups.

The process for refining a crude resin for an electronic materialaccording to the present invention is used for a crude resin for anelectronic material containing (a1) structural units derived from a(meth)acrylate ester with a hydrophilic site. These types of electronicmaterial crude resins are suited to use as the resin used in achemically amplified photoresist composition.

Examples of the resins that can be used in a chemically amplifiedphotoresist composition include the resin components of photoresistcompositions used with KrF or ArF excimer lasers, or even shorterwavelengths.

Electronic material crude resins that contain at least 20 mol %, andpreferably contain from 20 to 60 mol % of (a1) structural units derivedfrom a (meth)acrylate ester with a hydrophilic site are particularlyprone to the generation of oligomers and low molecular weight polymers,and particularly oligomers and low molecular weight polymers with acomparatively high polarity, and consequently the refining process ofthe present invention is particularly effective for such resins. If theabove structural unit content exceeds 60 mol % then the hydrophilicityof the crude resin increases, and the quantity of the resin removed withthe water layer during the washing step of the present invention becomesundesirably large.

There are no particular restrictions on (a1) the structural unitsderived from a (meth)acrylate ester with a hydrophilic site (hereafterreferred to as (a1) units), although preferred examples include thestructural units (a1-1) described below.

(a1-1) Structural units derived from a (meth)acrylate ester containing alactone unit (hereafter referred to as (a1-1) units).

(a1-1) Units:

An (a1-1) unit is a structural unit containing a lactone unit on theester side chain section of a (meth)acrylate ester. In the lactone unit,the ring containing the —O—C(O)— structure is counted as the first ring.Accordingly, the case in which the only ring structure is the ringcontaining the —O—C(O)— structure is referred to as a monocyclic group,and groups containing other ring structures are described as polycyclicgroups regardless of the structure of the other rings.

Examples of the (a1-1) structural unit include monocyclic groups inwhich one hydrogen atom has been removed from γ-butyrolactone, andpolycyclic groups in which one hydrogen atom has been removed from alactone containing polycycloalkane.

Specifically, the structural units represented by the structuralformulas (I) to (IV) shown below are preferred.

(wherein, R represents a hydrogen atom or a methyl group, and mrepresents either 0 or 1)

(wherein, R represents a hydrogen atom or a methyl group)

(wherein, R represents a hydrogen atom or a methyl group)

(wherein, R represents a hydrogen atom or a methyl group)

The above structural units (a1) preferably account for 20 to 60 mol %,and even more preferably from 30 to 50 mol % of the total of all thestructural units within the crude resin, as such proportions result insuperior resolution when the resin is used as a chemically amplifiedphotoresist resin.

A crude resin that is applicable to a refining process of the presentinvention utilizes a (meth)acrylate ester monomer with a hydrophilicsite, and preferably a (meth)acrylate ester monomer containing a lactoneunit, as the raw material monomer. When a crude resin is produced usingthis type of monomer, oligomers and low molecular weight polymerscomprising a high proportion of structural units containing this highlyhydrophilic lactone unit are generated as by-products.

If a conventional refining process is applied to this type of cruderesin containing these by-products, then removal of the above types ofhighly hydrophilic by-products is difficult, whereas if the refiningprocess of the present invention is employed, these highly hydrophilicby-products can be removed simply and effectively, enabling improvementsin the level of defects, and the storage stability of the resin, both ofwhich cause problems in chemically amplified photoresists.

A crude resin for an electronic material that is suitable for a refiningprocess of the present invention preferably comprises structural units(a2) described below in addition to the above structural units (a1).

(a2) Structural units derived from a (meth)acrylate ester containing ahydrophobic group (hereafter referred to as (a2) units).

(a2) Units:

The hydrophobic group within the unit (a2) refers to a highlyhydrophobic hydrocarbon group containing at least 6 carbon atoms, andpreferably 10 or more carbon atoms, contained within the ester sectionof the (meth)acrylate ester. The hydrocarbon group may be either achain-type or a cyclic hydrocarbon group, and specific examples includea hydrophobic group containing a tertiary alkyl group, a monocyclicgroup, or a polycyclic group. Of these, aliphatic type polycyclichydrocarbon groups are preferred, as they result in superior resolutionand dry etching resistance when the resin is used as a chemicallyamplified photoresist resin.

Examples of these (a2) units include the structural units (a2-1) and(a2-2) described below.

(a2-1) Structural units derived from a (meth)acrylate ester comprisingan acid dissociable, dissolution inhibiting group containing ahydrophobic aliphatic monocyclic or polycyclic group (hereafter referredto as (a2-1) units).

(a2-2) Structural units derived from a (meth)acrylate ester comprising anon-acid dissociable group containing a hydrophobic aliphatic polycyclicgroup (hereafter referred to as (a2-2) units).

The term “non-acid dissociable” used in the description of the (a2-2)units does not mean that the group is chemically completelynon-dissociable, but rather that the level of acid dissociability islower than that of an (a2-1) unit and results in no significant resistpatterning.

(a2-1) Units:

In terms of the acid dissociable, dissolution inhibiting groupcontaining an aliphatic monocyclic or polycyclic group that is used asthe hydrophobic group, suitable examples of the aliphatic monocyclicgroup include groups in which one hydrogen atom has been removed from acycloalkane. Examples of the aliphatic polycyclic group include groupsin which one hydrogen atom has been removed from a polycycloalkane suchas a bicycloalkane, a tricycloalkane or a tetracycloalkane.

Specific examples include groups in which one hydrogen atom has beenremoved from cyclohexane in the case of an aliphatic monocyclic group,and groups in which one hydrogen atom has been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane in the case of an aliphaticpolycyclic group.

This polycyclic group can be appropriately selected from the multitudeof acid dissociable, dissolution inhibiting groups proposed for usewithin ArF excimer laser photoresist composition resins.

Of these groups, cyclohexyl groups, adamantyl groups, norbornyl groups,and tetracyclododecanyl groups are preferred in terms of industrialavailability.

There are no particular restrictions on the above acid dissociable,dissolution inhibiting group, providing it is a group which can be usedin a resin for a positive chemically amplified photoresist composition,and which dissociates under the action of acid, causing the resin toshift from an alkali insoluble state to an alkali soluble state.

Typically, groups in which a cyclic or a chain-type tertiary alkyl esteris formed at the carboxyl group of the (meth)acrylic acid are the mostwidely used.

Specifically, the structural unit (a2-1) is preferably at least one unitselected from a group consisting of the general formulas (V) to (VII)shown below.

(wherein, R represents a hydrogen atom or a methyl group, and R¹represents a lower alkyl group)

(wherein, R represents a hydrogen atom or a methyl group, and R² and R³each represent, independently, a lower alkyl group)

(wherein, R represents a hydrogen atom or a methyl group, and R⁴represents a tertiary alkyl group)

Within the above formula, the group R¹ is preferably a straight chain orbranched alkyl group of 1 to 5 carbon atoms, and specific examplesinclude a methyl group, ethyl group, propyl group, isopropyl group,n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentylgroup and neopentyl group. Of these, an alkyl group of at least 2 carbonatoms, and preferably from 2 to 5 carbon atoms, is preferred as itprovides an acid dissociability that is greater than the case in whichR¹ is a methyl group, and enables higher sensitivity. From an industrialviewpoint, a methyl group or an ethyl group is preferred.

The aforementioned groups R² and R³ each preferably represent,independently, a lower alkyl group of 1 to 5 carbon atoms. These typesof groups tend to display a higher acid dissociability than a2-methyl-2-adamantyl group.

Specifically, the groups R² and R³ preferably each represent,independently, the same types of straight chain or branched lower alkylgroups described above for R¹. Of these groups, the case in which R² andR³ are both methyl groups is preferred in terms of industrialavailability, and specific examples of the structural unit representedby the formula (VI) include structural units derived from2-(1-adamantyl)-2-propyl (meth)acrylate.

The group R⁴ represents a tertiary alkyl group such as a tert-butylgroup or a tert-amyl group, although a tert-butyl group is preferred interms of industrial availability.

Furthermore, the group —COOR⁴ may be bonded to either position 3 or 4 ofthe tetracyclododecanyl group shown in the formula, although a mixtureof both stereoisomers results, and so the bonding position cannot befurther specified. Furthermore, the carboxyl group residue of the(meth)acrylate structural unit may be bonded to either position 8 or 9,although similarly, the bonding position cannot be further specified.

The above structural units (a2-1) preferably account for 20 to 60 mol %,and even more preferably from 30 to 50 mol % of the total of all thestructural units within the resin, as such proportions result insuperior resolution when the resin is used as a chemically amplifiedphotoresist resin.

(a2-2) Units:

(a2-2) units comprise a non-acid dissociable group containing ahydrophobic aliphatic polycyclic group.

Examples of the aliphatic polycyclic group include the same groupsdescribed above in relation to the (a2-1) units, and any of themultitude of conventional groups proposed for use within ArF excimerlaser photoresist composition resins can be used.

From the viewpoint of industrial availability, at least one of atricyclodecanyl group, an adamantyl group or a tetracyclododecanyl groupis preferred.

Specific examples of the (a2-2) unit include the units with thestructures (VIII) to (X) shown below.

(wherein, R represents a hydrogen atom or a methyl group)

(wherein, R represents a hydrogen atom or a methyl group)

(wherein, R represents a hydrogen atom or a methyl group)

The above structural units (a2-2) preferably account for 1 to 30 mol %,and even more preferably from 5 to 20 mol % of the total of all thestructural units within the resin, as such proportions result inexcellent resolution for isolated patterns through to semi densepatterns when the resin is used as a chemically amplified photoresistresin.

In those cases where the crude resin to which the refining process ofthe present invention is applied is a resin comprising the (a1) unitsand (a2) units described above, the raw material monomers are a monomercontaining a lactone unit with a comparatively high level ofhydrophilicity, and a monomer with a hydrophobic group. When productionof a crude resin is conducted using these monomers, highly hydrophilicoligomers and low molecular weight polymers comprising a largeproportion of structural units containing a lactone unit, and highlyhydrophobic oligomers and low molecular weight polymers comprising alarge proportion of structural units containing a hydrophobic group areboth generated as by-products.

If a conventional refining process is applied to this type of cruderesin containing by-products, then removal of both of the above types ofby-products is difficult, and in such cases, refining is preferablyconducted by using a combination of both a washing step of the presentinvention and a hydrophobic solvent washing step. By first conducting awashing step of the present invention as described above, any highpolarity by-products can be removed simply and effectively. Bysubsequently conducting an aforementioned hydrophobic solvent washingstep, any highly hydrophobic by-products can be effectively removed,enabling a further improvement in the defect reduction effect.

Suitable resins for use with a refining process of the present inventionmay also comprise another structural unit (a3) in addition to the (a1)units and (a2) units described above.

There are no particular restrictions on the unit (a3), provided itcannot be classified as one of the above units (a1) and (a2). Forexample, structural units derived from a (meth)acrylate ester comprisinga hydroxyl group containing aliphatic polycyclic group are preferred.

The aliphatic polycyclic group may be appropriately selected from theplurality of polycyclic groups listed in the description of the abovestructural unit (a1).

Specifically, hydroxyl group containing adamantyl groups or carboxylgroup containing tetracyclododecanyl groups are preferred as thestructural unit (a3).

More specific examples include the structural units represented by thegeneral formula (XI) shown below. The above (a3) units preferablyaccount for 5 to 50 mol %, and even more preferably from 10 to 40 mol %of the total of all the structural units within the resin, as suchproportions result in a superior resist pattern shape when the resin isused as a chemically amplified photoresist resin.

(wherein, R represents a hydrogen atom or a methyl group, and nrepresents an integer of 1 to 3)

In addition, an aforementioned crude resin for an electronic materialmay comprise two types of units, namely, acrylate ester units andmethacrylate ester units, and combinations of these two units results inthree types of crude resin, namely, resins containing only acrylateester units, resins containing only methacrylate ester units, and resinscontaining both units.

The refining process of the present invention is particularly suited toresins containing only structural units derived from methacrylateesters, and resins containing from 20 to 70 mol % of structural unitsderived from acrylate esters, and from 30 to 80 mol % of structuralunits derived from methacrylate esters.

In addition, the latter type of resins containing structural unitsderived from acrylate esters and structural units derived frommethacrylate esters in a specific ratio are prone to the production ofoligomer and low molecular weight polymer by-products of differingpolarity, due to the difference in polarity of the structural unitsderived from acrylate esters and the structural units derived frommethacrylate esters, although these types of by-products can also beeffectively removed using a refining process of the present invention.

As follows is a description of a chemically amplified photoresistcomposition that can be readily produced using an electronic materialresin obtained by the refining process of the present inventiondescribed above.

This chemically amplified photoresist composition comprises (A) a resincomponent (hereafter referred to as component (A)), (B) an acidgenerator component that generates acid on exposure (hereafter referredto as component (B)), and (C) an organic solvent (hereafter referred toas component (C)). In those cases when an electronic material resin ofthe present invention is used for a photoresist composition, the resinis used for the component (A) which is either an alkali soluble resin ora resin that can be converted to an alkali soluble state. The formercase is a so-called negative photoresist composition, and the lattercase a so-called positive photoresist composition.

In the case of a negative type composition, a cross linking agent isadded to the photoresist composition with the component (B). Then,during resist pattern formation, when acid is generated from thecomponent (B) by exposure, this acid acts on the cross linking agent,causing cross linking between the component (A) and the cross linkingagent, and making the composition alkali insoluble. The cross linkingagent typically uses either a compound with a methylol group or an alkylether thereof, including amino based resins such as melamine resin, urearesin or glycoluril resin.

In the case of a positive type composition, the component (A) is analkali insoluble compound with a so-called acid dissociable, dissolutioninhibiting group, and when acid is generated from the component (B) byexposure, this acid causes the acid dissociable, dissolution inhibitinggroup to dissociate, making the component (A) alkali soluble. In thiscase, the resin must comprise (a1) units and (a2-1) units.

Component (A):

The above types of electronic material resins, obtained using theprocess for refining an electronic material crude resin according to thepresent invention, are used.

There are no particular restrictions on the polystyrene equivalentweight average molecular weight of the component (A), as determined byGPC, although values within a range from 5,000 to 30,000 are preferred,and values from 8,000 to 20,000 are even more desirable.

Furthermore, the component (A) can be formed from either one, or two ormore different resins, and for example, may utilize one, or two or moreof the above types of resins comprising units derived from(meth)acrylate esters as the principal components, or may also utilize amixture with other conventional photoresist composition resins.

Component (B):

The component (B) can be appropriately selected from known materialsused as acid generators in conventional positive and negative chemicallyamplified resists.

Specific examples include onium salts such as diphenyliodoniumtrifluoromethanesulfonate, (4-methoxyphenyl)phenyliodoniumtrifluoromethanesulfonate, bis(p-tert-butylphenyl)iodoniumtrifluoromethanesulfonate, triphenylsulfonium trifluoromethanesulfonate,(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,(4-methylphenyl)diphenylsulfonium nonafluorobutanesulfonate,(p-tert-butylphenyl)diphenylsulfonium trifluoromethanesulfonate,diphenyliodonium nonafluorobutanesulfonate,bis(p-tert-butylphenyl)iodonium nonafluorobutanesulfonate andtriphenylsulfonium nonafluorobutanesulfonate. Of these, onium salts witha fluorinated alkylsulfonate ion as the anion are preferred.

This component (B) may utilize a single compound, or a combination oftwo or more compounds. The quantity of the component (B) is typicallywithin a range from 0.5 to 30 parts by weight per 100 parts by weight ofthe component (A).

Component (C):

The component (C) can be any solvent capable of dissolving the component(A) and the component (B) to generate a uniform solution, and thesolvent used can be one, or two or more solvents selected from amongstknown solvents used for conventional chemically amplified resists.

Specific examples of the solvent include ketones such as acetone, methylethyl ketone, cyclohexanone, methyl isoamyl ketone and 2-heptanone;polyhydric alcohols and derivatives thereof such as ethylene glycol,ethylene glycol monoacetate, diethylene glycol, diethylene glycolmonoacetate, propylene glycol, propylene glycol monoacetate, dipropyleneglycol, or the monomethyl ether, monoethyl ether, monopropyl ether,monobutyl ether or monophenyl ether of dipropylene glycol monoacetate;cyclic ethers such as dioxane; and esters such as methyl lactate, ethyllactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate,ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate.These organic solvents can be used singularly, or as a mixed solvent oftwo or more different solvents.

Of these solvents, propylene glycol monomethyl ether acetate (PGMEA) andethyl lactate (EL) and the like are preferred.

The quantity of the component (C) is sufficient to generate aconcentration that is suitable for use as a photoresist composition, andenables application of the composition to a substrate or the like. Thequality of the component (C) in the photoresist composition is such asto produce a totally combined solid fraction concentration of 3 to 50%by weight, and preferably from 7 to 20% by weight, in accordance withthe resist application thickness.

Other Components:

Other components may also be added to the photoresist compositionaccording to need.

For example, in order to improve the resist pattern shape and the longterm stability (post exposure stability of the latent image formed bythe pattern wise exposure of the resist layer), an amine, andparticularly a secondary lower aliphatic amine or a tertiary loweraliphatic amine, can also be added as an optional component (D).

Here, a lower aliphatic amine refers to an alkyl or alkyl alcohol amineof no more than 5 carbon atoms, and examples of these secondary andtertiary amines include trimethylamine, diethylamine, triethylamine,di-n-propylamine, tri-n-propylamine, tripentylamine, diethanolamine andtriethanolamine, and alkanolamines such as triethanolamine areparticularly preferred.

These may be used singularly, or in combinations of two or moredifferent compounds.

This amine is typically added in a quantity within a range from 0.01 to5.0 parts by weight per 100 parts by weight of the component (A).

Furthermore, in order to improve the resist pattern shape and the longterm stability in a similar manner to the component (D), an organiccarboxylic acid, or a phosphorus oxo acid or derivative thereof can alsobe added as an optional component (E). Either one, or both of thecomponent (D) and the component (E) can be used.

Examples of suitable organic carboxylic acids include malonic acid,citric acid, malic acid, succinic acid, benzoic acid, and salicylicacid.

Examples of suitable phosphorus oxo acids or derivatives thereof includephosphoric acid or derivatives thereof such as esters, includingphosphoric acid, di-n-butyl phosphate, and diphenyl phosphate;phosphonic acid or derivatives thereof such as esters, includingphosphonic acid, dimethyl phosphonate, di-n-butyl phosphonate,phenylphosphonic acid, diphenyl phosphonate and dibenzyl phosphonate;and phosphinic acid or derivatives thereof such as esters, includingphosphinic acid and phenylphosphinic acid, and of these, phosphonic acidis particularly preferred.

The component (E) is typically used in a quantity within a range from0.01 to 5.0 parts by weight per 100 parts by weight of the component(A).

Miscible additives can also be added to a photoresist composition of thepresent invention according to need, including additive resins forimproving the properties of the resist film, surfactants for improvingthe ease of application, dissolution inhibitors, plasticizers,stabilizers, colorants and halation prevention agents.

Production of the chemically amplified photoresist composition can beconducted by simply mixing and stirring each of the components togetherusing conventional methods, and where required, the composition may alsobe mixed and dispersed using a dispersion device such as a dissolver, ahomogenizer, or a triple roll mill. Furthermore, following mixing, thecomposition may also be filtered using a mesh or a membrane filter orthe like.

Particularly in the case of a positive photoresist composition for usewith an ArF excimer laser, a resin containing both (a1) units and (a2-1)units must be used, and resins that also contain (a3) units, and in somecases (a2-2) units, are preferred as they provide superiorcharacteristics of sensitivity, resolution, and resist pattern shape. Inthose cases when this type of resin, formed by the polymerization ofmonomers of differing polarity, is used, it is thought that variousmonomers, oligomers and other by-products within the resin have adeleterious effect on the long term stability of the photoresistcomposition. Accordingly, a chemically amplified photoresist compositionproduced using an electronic material resin according to the presentinvention displays favorable storage stability as a resist solution, andis less likely to produce defects during resist pattern formation.

The storage stability as a resist solution is evaluated using a liquidparticle counter (brand name: Particle Sensor KS-41, manufactured byRion Co., Ltd.), using a photoresist composition sample that has beenstored at room temperature following production. The above counter is adevice for counting the number of particles with a particle diameter ofat least 0.2 μm, within each 1 cm³. The measurement limit is typicallyapproximately 20,000 particles/cm³.

The quantity of impurities within a photoresist composition immediatelyfollowing production is typically restricted to no more than 10particles/cm³. By utilizing the present invention, the storage stabilityas a resist solution after storage for half a year is preferablyessentially unchanged from the stability immediately followingproduction.

A resist pattern using the above type of photoresist composition can beformed using typical methods.

For example, a photoresist composition described above is first appliedto the surface of a substrate such as a silicon wafer using a spinner orthe like, and a prebake (heat treatment prior to exposure) is conductedunder temperature conditions of 80 to 150° C. for 40 to 120 seconds, andpreferably for 60 to 90 seconds. Following selective exposure of theresist film with an exposure apparatus, by irradiating KrF, ArF or F₂excimer laser light, or other radiation such as extreme UV, EB (electronbeam) or X-ray radiation, through a desired mask pattern, PEB (postexposure baking) is conducted under temperature conditions of 80 to 150°C. for 40 to 120 seconds, and preferably for 60 to 90 seconds.Subsequently, developing is conducted using an alkali developing liquidsuch as an aqueous solution of tetramethylammonium hydroxide with aconcentration of 0.1 to 10% by weight. In this manner, a resist patternthat is faithful to the mask pattern can be obtained.

An organic or inorganic anti-reflective film may also be providedbetween the substrate and the applied layer of the resist composition.

Defects within the resist pattern can be evaluated by the number ofso-called surface defects, measured using, for example, a KLA2132 (brandname) surface defect observation apparatus manufactured by KLA TencorCorporation.

EXAMPLES

As follows is a more detailed description of the present invention usinga series of examples.

The physical properties of the photoresist compositions in each of thefollowing examples and comparative examples were determined in thefollowing manner.

(1) Storage Stability as a Resist Solution

The storage stability as a resist solution of a photoresist compositionthat had been stored at room temperature following production wasevaluated using a liquid particle counter (brand name: KS-41,manufactured by Rion Co., Ltd.).

Measurement upper limit is approximately 20,000 particles/cm³.

Furthermore, the quantity of impurities within a photoresist compositionimmediately following production was restricted to no more thanapproximately 10 particles/cm³.

(2) Defects

The prepared photoresist composition (a positive type composition) wasapplied to a silicon wafer (diameter 200 mm) using a spinner, and wasthen prebaked and dried on a hotplate at 130° C. for 90 seconds, forminga resist layer with a film thickness of 350 nm.

Subsequently, this layer was selectively irradiated with an ArF excimerlaser (193 nm) through a mask pattern, using an ArF exposure apparatusNSR-S302 (manufactured by Nikon Corporation, NA (numericalaperture)=0.60, σ=0.75).

The irradiated resist was then subjected to PEB treatment at 120° C. for90 seconds, subsequently subjected to puddle development for 60 secondsat 23° C. in a 2.38% by weight aqueous solution of tetramethylammoniumhydroxide, and was then washed for 20 seconds with water, and dried,forming a 250 nm line and space pattern.

The number of defects was then measured using a KLA2132 (brand name)surface defect observation apparatus manufactured by KLA TencorCorporation, thus evaluating the number of defects within the wafer.Three wafers were used in each example and comparative example, and theaverage value was reported.

Example 1

The monomers (1) to (3) described below were dissolved in 400 ml oftetrahydrofuran, 1.64 g of azobisisobutyronitrile was added as areaction initiator, and a polymerization reaction was conducted for 3hours at 70° C.

-   (1) 16.64 g (40 mol %) of norbornanelactone acrylate (the monomer    corresponding with the structural unit (a1), and equivalent to the    monomer unit of the above formula (II) wherein R is a hydrogen atom)-   (2) 19.84 g (40 mol %) of 2-ethyl-2-adamantyl methacrylate    (corresponding with the structural unit (a2-1))-   (3) 8.88 g (20 mol %) of 3-hydroxy-1-adamantyl acrylate    (corresponding with the structural unit (a3))

Following completion of the polymerization, the reaction liquid waspoured into 2500 ml of n-heptane, the resulting mixture was stirred for30 minutes at 25° C., and the precipitated solid was collected byfiltration. This solid was then redissolved in 400 ml oftetrahydrofuran, poured into 2500 ml of heptane, the resulting mixturewas stirred for 30 minutes at 25° C., and the precipitated crude resinwas collected by filtration.

30 g of the crude resin obtained in the manner described above wasdissolved in 345 ml of PGMEA to form an 8% solution, 150 ml of water wasadded thereto, the mixture was stirred for 5 minutes at 25° C., andfollowing separation of the two layers, the water layer was removed. Afurther 150 ml of water was then added, the mixture was stirred for 10minutes at 25° C., and following separation of the two layers, the waterlayer was once again removed. The resulting PGMEA layer was concentratedand any remaining water removed by distillation, yielding a resin (A-1)for an electronic material. The weight average molecular weight of (A-1)was 20,000.

Analysis of the components extracted from the water layers revealedoligomers of the aforementioned (1), (2) and (3) with molecular weightsof less than 1500, in which the mol % values for the units were outsidethe above specified ratios, and highly hydrophilic oligomers containingmore than 40 mol % of units of the component (1).

The components (A) to (D) described below were mixed together anddissolved to prepare a chemically amplified photoresist composition (apositive composition for use with an ArF excimer laser).

-   Component (A): 100 parts by weight of (A-1) obtained above-   Component (B): 3.0 parts by weight of triphenylsulfonium    nonafluorobutanesulfonate.-   Component (C): 800 parts by weight of a mixed solvent of PGMEA and    propylene glycol monomethyl ether (weight ratio 6:4)-   Component (D): 0.2 parts by weight of triethanolamine

The storage stability as a resist solution of the photoresistcomposition after storage for 6 months at room temperature wasessentially unchanged from the stability observed immediately followingproduction.

The number of defects averaged no more than 5 defects per wafer. Using ameasuring SEM S-9220 (manufactured by Hitachi, Ltd.), the defects wereidentified as so-called bridge type defects in which bridging occursbetween line patterns.

Comparative Example 1

With the exception of not conducting the washing operation using PGMEAand water described in the example 1, a resin (A′-1) for an electronicmaterial was produced in the same manner as the example 1. Subsequently,a photoresist was prepared in the same manner as the example 1 with theexception of replacing (A-1) with (A′-1).

As a result, the storage stability as a resist solution following twoweeks storage at room temperature exceeded the measurement limit and wasunable to be accurately measured.

The number of defects averaged approximately 60,000 defects per wafer.Using the aforementioned measuring SEM device, the defects wereidentified as so-called bridge type defects in which bridging occursbetween line patterns.

Examples 2 to 7

With the exceptions of altering each of the monomers (1), (2) and (3),and altering the molar ratio of the reactants as shown in Table 1, cruderesins were obtained by conducting polymerization reactions in the samemanner as the example 1. Subsequently, refined resins were produced in asimilar manner to the example 1, by performing a hydrophobic solventwashing step using n-heptane, and a subsequent washing step of thepresent invention using PGMEA and water. TABLE 1 Example MonomerDescription of each monomer and molar ratio units (a1) units (a2-1)units (a3) units (a2-2) units Crude norbornanelactone2-ethyl-2-adamantyl 3-hydroxy-1-adamantyl None resin of acrylate(corresponds with methacrylate acrylate (corresponds with example 1 themonomer unit of the (corresponds with the the monomer unit of theformula (II) wherein R is a monomer unit of the formula (XI) wherein Ris hydrogen atom, hereafter formula (V) wherein R is a hydrogen atom,and a abbreviated NorLac-Ac) a methyl group and R′ is single hydroxylgroup is 40 mol % an ethyl group, hereafter bonded to position 3 of theabbreviated EthAd-Mc) adamantyl group, 40 mol % hereafter abbreviated asADOH-Ac) 20 mol % Crude NorLac-Ac EthAd-Mc ADOH-Ac Tetracyclodecanylresin of 40 mol % 25 mol % 15 mol % methacrylate example 2 (correspondswith the monomer unit of the formula (X) wherein R is a methyl group,hereafter abbreviated as TCD-Mc) 5 mol % Crude NorLac-Ac EthAd-McADOH-Ac None resin of 50 mol % 30 mol % 20 mol % example 3 Crudeγ-butyrolactone 2-methyl-2-adamantyl 3-hydroxy-1-adamantyl TCD-Mc resinof methacrylate methacrylate methacrylate 15 mol % example 4(corresponds with the (corresponds with the (corresponds with themonomer unit of the monomer unit of the monomer unit of the formula (IV)wherein R is formula (V) wherein R is formula (XI) wherein R is a methylgroup, hereafter a methyl group and R′ is a a methyl group, and aabbreviated as methyl group, hereafter single hydroxyl group isγBuLac-Mc) abbreviated MethAd-Mc) bonded to position 3 of the 35 mol %35 mol % adamantyl group, hereafter abbreviated as ADOH-Mc) 15 mol %Crude γBuLac-Mc MethAd-Mc ADOH-Mc TCD-Mc resin of 40 mol % 40 mol % 15mol % 5 mol % example 5 Crude norbornanelactone EthAd-Mc ADOH-Mc Noneresin of acrylate (corresponds with 40 mol % 20 mol % example 6 themonomer unit of the formula (III) wherein R is a methyl group) 40 mol %Crude NorLac-Ac 2-(1-adamantyl)-2-propyl ADOH-Mc None resin of 50 mol %methacrylate 20 mol % example 7 (corresponds with the monomer unit ofthe formula (VI) wherein R, R², R³ are methyl groups, hereafterabbreviated iPrAd-Mc) 30 mol %

Subsequently, chemically amplified photoresist composition, and thestorage stability as a resist solution and the defects were measured foreach composition in the same manner as the example 1. The results areshown in Table 3. TABLE 2 Photoresist Composition (B) Acid generator (C)Organic solvent Example (A) Resin component component component (D)Amine component Example 1 Refined resin produced triphenylsulfoniumPGMEA/PGME triethanolamine from crude resin of nonafluorobutanesulfonate(weight ratio 4:6) 0.2 parts by weight example 1 (hereafter abbreviatedas 800 parts by weight 100 parts by weight TPS-NFBS) 3.0 parts by weightExample 2 Refined resin produced TPS-NFBS EL/PGMEA triethanolamine fromcrude resin of 3.0 parts by weight (weight ratio 4:6) 0.2 parts byweight example 2 800 parts by weight 100 parts by weight Example 3Refined resin produced TPS-NFBS EL/PGMEA triethanolamine from cruderesin of 3.0 parts by weight (weight ratio 4:6) 0.2 parts by weightexample 3 800 parts by weight 100 parts by weight Example 4 Refinedresin produced TPS-NFBS PGMEA triethanolamine from crude resin of 2.0parts by weight 800 parts by weight 0.2 parts by weight example 4 100parts by weight Example 5 Refined resin produced TPS-NFBS EL/PGMEAtriethanolamine from crude resin of 3.0 parts by weight (weight ratio4:6) 0.2 parts by weight example 5 800 parts by weight 100 parts byweight Example 6 Refined resin produced TPS-NFBS EL/PGMEAtriethanolamine from crude resin of 3.0 parts by weight (weight ratio4:6) 0.2 parts by weight example 6 800 parts by weight 100 parts byweight Example 7 Refined resin produced TPS-NFBS EL/PGMEAtriethanolamine from crude resin of 3.0 parts by weight (weight ratio4:6) 0.2 parts by weight example 7 800 parts by weight 100 parts byweight

TABLE 3 Evaluation Items Example Storage stability as a resist solutionDefects Example 1 After storage for 6 months at room Average of no morethan 5 defects per wafer temperature, essentially unchanged fromstability immediately following production. Example 2 After storage for1 month at room temperature, Average of no more than 10 defects perwafer essentially unchanged from stability immediately followingproduction. Example 3 After storage for 1 month at room temperature,Average of no more than 10 defects per wafer essentially unchanged fromstability immediately following production. Example 4 After storage for3 months at room Average of no more than 5 defects per wafertemperature, essentially unchanged from stability immediately followingproduction. Example 5 After storage for 4 months at room Average of nomore than 6 defects per wafer temperature, essentially unchanged fromstability immediately following production. Example 6 After storage for4 months at room Average of no more than 6 defects per wafertemperature, essentially unchanged from stability immediately followingproduction. Example 7 After storage for 3 months at room Average of nomore than 5 defects per wafer temperature, essentially unchanged fromstability immediately following production.

Comparative Examples 2 to 7

With the exception of performing only the hydrophobic solvent washingstep using n-heptane, and omitting the washing step of the presentinvention using PGMEA and water, crude resins were produced in the samemanner as the examples 2 to 7, and using these crude resins, positivephotoresist compositions were then prepared in the same manner as theexamples 2 to 7.

Subsequently, the storage stability as a resist solution and the defectswere measured for each composition in the same manner as the example 1.The results are shown in Table 4. TABLE 4 Comparative Evaluation ItemsExample Storage stability as a resist solution Defects Comparative Afterstorage for 2 weeks at room temperature, Average of approximately 60,000Example 1 measurement limit was exceeded, NG defects per waferComparative After storage for 1 month at room temperature, Average ofapproximately 60,000 Example 2 measurement limit was exceeded, NGdefects per wafer Comparative After storage for 1 month at roomtemperature, Average of approximately 60,000 Example 3 measurement limitwas exceeded, NG defects per wafer Comparative After storage for 1 monthat room temperature, Average of approximately 3000 defects Example 4measurement limit was exceeded, NG per wafer Comparative After storagefor 1 month at room temperature, Average of approximately 60,000 Example5 measurement limit was exceeded, NG defects per wafer Comparative Afterstorage for 1 month at room temperature, Average of approximately 60,000Example 6 measurement limit was exceeded, NG defects per waferComparative After storage for 1 month at room temperature, Average ofapproximately 60,000 Example 7 measurement limit was exceeded, NGdefects per wafer

From the results of the examples and comparative examples describedabove it is evident that in the examples according to the presentinvention, employment of a washing step of the present invention enablesthe effective removal of by-products from the resin, and as a result,the storage stability as a resist solution of a photoresist compositionproduced using the resin improves markedly. The quantity of defects onformation of a resist pattern is also markedly reduced.

INDUSTRIAL APPLICABILITY

The present invention provides a process for effectively removingby-products such as oligomers contained within a crude resin for anelectronic material, thus producing a resin for an electronic material,as well as a resin for an electronic material produced by such aprocess, a process for producing a chemically amplified photoresistcomposition using such a resin for an electronic material, and achemically amplified photoresist composition comprising such a resin foran electronic material, and is consequently extremely useful inindustry.

1. A process for refining a crude resin for an electronic material,wherein a crude resin for an electronic material containing (a1)structural units derived from a (meth)acrylate ester with a hydrophilicsite is washed using (b1) an organic solvent which is capable ofdissolving said crude resin for an electronic material and whichseparates into two layers when combined with water, and (b2) water.
 2. Aprocess for refining a crude resin for an electronic material accordingto claim 1, wherein said organic solvent (b1) is at least one solventselected from a group consisting of glycol ether esters, esters andketones.
 3. A process for refining a crude resin for an electronicmaterial according to claim 1, wherein said organic solvent (b1) is atleast one solvent selected from a group consisting of propylene glycolmonoalkyl ether acetate, ethyl acetate, butyl acetate, isoamyl acetate,2-heptanone, methyl ethyl ketone, methyl-isobutyl ketone, andcyclohexanone.
 4. A process for refining a crude resin for an electronicmaterial according to claim 3, wherein said propylene glycol monoalkylether acetate is propylene glycol monomethyl ether acetate.
 5. A processfor refining a crude resin for an electronic material according to claim1, wherein prior to, following, or both prior to and following saidwashing, said crude resin for an electronic material is washed using ahydrophobic solvent.
 6. A process for refining a crude resin for anelectronic material according to claim 1, wherein said crude resin foran electronic material is a resin used for preparing a chemicallyamplified photoresist composition.
 7. A process for refining a cruderesin for an electronic material according to claim 1, wherein saidcrude resin for an electronic material comprises at least 20 mol % ofsaid (a1) units.
 8. A process for refining a crude resin for anelectronic material according to claim 1, wherein said hydrophilic siteis a lactone unit.
 9. A process for refining a crude resin for anelectronic material according to claim 1, wherein said crude resin foran electronic material is a resin comprising said (a1) units and (a2)structural units derived from a (meth)acrylate ester containing ahydrophobic group.
 10. A process for refining a crude resin for anelectronic material according to claim 9, wherein said hydrophobic groupin said (a2) units is an aliphatic polycyclic hydrocarbon group.
 11. Aprocess for refining a crude resin for an electronic material accordingto claim 1, wherein said crude resin for an electronic materialcomprises from 20 to 60 mol % of said (a1) units, and from 5 to 50 mol %of said (a2) units.
 12. A process for refining a crude resin for anelectronic material according to claim 1, wherein said crude resin foran electronic material is a resin formed solely from structural unitsderived from a methacrylate ester.
 13. A process for refining a cruderesin for an electronic material according to claim 1, wherein saidcrude resin for an electronic material comprises from 20 to 70 mol % ofstructural units derived from an acrylate ester, and from 30 to 80 mol %of structural units derived from a methacrylate ester.
 14. A process forrefining a crude resin for an electronic material according to claim 1,wherein during said washing, said crude resin for an electronic materialis dissolved in said organic solvent (b1), water (b2) is then added, andfollowing separation into two layers, a water layer is removed.
 15. Aresin for an electronic material produced by a process according toclaim
 1. 16. A process for producing a chemically amplified photoresistcomposition using a resin for an electronic material according to claim15.
 17. A chemically amplified pkotoresist composition comprising aresin for an electronic material according to claim 15.